


the invariant of the algorithm

by orestes



Category: Teen Wolf (TV)
Genre: Alternate Universe, Fluff, Getting Together, M/M, Mutual Pining, Robots, Science, Scientist Derek, Scientist Stiles Stilinski
Language: English
Status: Completed
Published: 2015-04-13
Updated: 2015-04-13
Packaged: 2018-03-22 18:28:21
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 7,228
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/3738907
Author URL: https://archiveofourown.org/users/orestes/pseuds/orestes
Summary: <blockquote class="userstuff">
              <p>If Stiles were a projectile and ambition were a quantifiable force, the trajectory graph of his life would start at the summer he went to robotics camp for the first time, hit a turning point the day he got his acceptance letter from MIT, then hurtle straight towards the world’s leading corporate science facility.</p>
            </blockquote>





	the invariant of the algorithm

**Author's Note:**

  * For [boyfriends](https://archiveofourown.org/users/boyfriends/gifts).



> i have about six WIPs on-the-go at the moment. it's nice to finally have something complete! the title is something that caught my eye when i searched "bad science pick-up lines" on google. thank you to bandsiwishimeet for the beta & to becca (as ever) for keeping my awful spelling in check.
> 
> disclaimer: i am not a scientist. i love science and i always try to keep up to date with science-related things, but i am not a scientist, i am a literature student. so... you know. don't take the science-y stuff in this fic too seriously.

If Stiles were a projectile and ambition were a quantifiable force, the trajectory graph of his life would start at the summer he went to robotics camp for the first time, hit a turning point the day he got his acceptance letter from MIT, then hurtle straight towards the world’s leading corporate science facility.

Stiles submitted a proposal to The Beacon three months before he graduated, mostly as homage to the pipe-dream fantasy of working there he clung to as a kid, but he never expected anything to come of it. Commercial science is a highly competitive field. You need to have years of experience under your belt before most major corporations will even consider you. No one gets handed an entry level job at a company like that.

Or so he thought.

But here he is, two weeks out of college, sitting on an uncomfortable stool in a windowless room full of potential candidates, waiting to be called to his interview.

This is the cumulative result of everything Stiles has ever achieved.

Stiles is trying hard not to let himself get overwhelmed by how _big_ this is. So far it seems to be working. He’s been here for almost an hour already, and he still hasn’t started to doubt himself enough to bust open the manila folder on his lap to check over every word, every measurement, and every angle that’s written on his proposal.

The worst thing he could do right now is psych himself out, and trying to read over anything would be the fastest way to ensure that happens, so Stiles leaves that can of worms alone and distracts himself by playing spot-the-hidden-surveillance-camera on the walls.

He manages to find twenty-seven before his name is called.

The interview itself passes in a blur. Stiles pitches his ideas to three suits and two scientists, talking them through his carefully constructed diagrams, his algorithms, his codes, and then answers questions about the logistics and potential costs of making a functional prototype.

He knows he should focus on the commercial aspect of the project, since his audience is clearly more interested in the business side of things than they are in the mechanics behind it, but he gets carried away talking about the science.

He’s pretty sure he ends up kind of rambling at them.

He spends most of the five hour drive back to his hometown thinking of better ways he could have phrased his ideas, remembering things he should have mentioned, and metaphorically kicking himself for just about everything.

“How did you get on, son?” his dad asks when Stiles finally lets himself into the house.

Stiles knows his dad must be exhausted. Parrish is on vacation, so he worked the morning shift at the Sheriff’s department every day last week. It must have taken some willpower—and a hell of a lot of caffeine, if the stale smell of coffee lingering in the house and the collection of empty mugs stacked up on the draining board in the kitchen are to be trusted—for him to stay awake this late.

But he waited up to talk to Stiles anyway, and Stiles is grateful for it.

Stiles feels the tight knot of anxiety in his chest relax just from seeing him.

“I don’t know,” Stiles replies honestly. “It could have been better, I guess, but at the same time it could have been worse.” He runs a hand through his hair and sighs. “I don’t think I’m gonna get the placement, but at least I gave it my best shot, right?”

His dad pats the empty space on the couch beside him.

“Whatever comes of this,” he says, “I’m really proud of you, kid.”

That night Stiles falls asleep with his face buried in his dad’s shoulder.

A week later he gets a call to say he got the job.

*

“Time to go, buddy,” Stiles announces from the door of the break room at the back of the lab. Isaac glances over at him and smirks. He’s sitting on the couch eating a pack of instant ramen, Scott’s head pillowed against his stomach. Stiles rolls his eyes and strides closer, pulling Scott upright by the wrist. “Come on.”

Scott lets Stiles manoeuvre him but keeps his eyes firmly shut, feigning sleep. He’s been pulling this since Erica showed him a nature documentary about hibernation and he worked out that sleep is just the human version of recharging. Scott doesn’t know that his body goes still and lifeless when his batteries run out, so he mimics the way Stiles acts when he’s asleep: muscles pliant, eyes shut, minimal response to external stimuli, occasional soft snores.

He conducted his research over the period of a week, prodding and poking Stiles awake every few hours before carefully writing down his ‘results’. Stiles probably would have been a hell of a lot more excited about the high levels of intuition that shows if the process hadn’t resulted in so many sleepless nights for him.

“Dude,” he says, flicking Scott hard between the eyes. “I know you’re online.”

Scott jerks away, his neutral expression slipping into an irritated scowl when his eyes snap open by reflex. Stiles only got around to fixing the glitches in his reflex codes a couple of months ago, and Scott isn’t used to them yet.

He rubs his forehead. “I hate when you do that.”

“And I hate when you don’t listen to me,” Stiles replies. “Get up. You need an update.”

Scott groans.

He used to like having his codes reprogrammed, but now it’s a chore to convince him to so much as set foot in the workshop. He hates having his systems shut down and his mind adjusted, hates the tweaks and the new features, and hates how vulnerable the whole process leaves him.

Stiles doesn’t blame him. The smallest glitch in an update can have any number of unexpected and awful effects on Scott’s internal systems, from erasing parts of his memories to slowing his motor functions to half their usual speed. On one particularly memorable occasion, Stiles messed up the coding so badly that Scott ended up offline for an entire week.

“We were about to play Mario Kart,” Isaac says, inclining his head towards the beat-up Wii in the corner of the room. “Can’t the update wait until tomorrow?”

“No. This update is too important to wait.”

Scott frowns. “Dude, I’m not due another upgrade for at least another month.”

“Yeah, but this isn’t just any upgrade.” Stiles stuffs his hands in the pockets of his jeans and rocks back on the heels of his feet, playing for casual. “This is an installation, bro.”

Scott’s eyes go wide with panic. “What? No. Stiles, I already told you I don’t want you to make me another weaponized arm. I’m not interested in blasting anyone with fireballs, and if you—”

“Why is that always your reaction to everything?” Stiles asks, cutting Scott off before he can start another rant about how he’s a sentient being, not a toy. “I equipped your hands with blasters one time, Scott, and you shouted at me until I took them out and destroyed them.”

“Yeah, because I don’t want to be—”

“Abducted by the secret services and forced to spend your life out in the field,” Stiles finishes for him, rolling his eyes. “I know. You’ve given me that speech a million and one times already. Now, do you want me to liberate you from your battery pack, or not?”

There’s a beat of silence.

“Oh my god.” Scott’s mouth drops open in awe. It’s one of the few habits he’s ever picked up from Stiles. “Are you for real?” Scott fumbles up from the couch so he can thump Stiles hard in the arm. “I can’t believe you finished the reactor without telling me!”

Stiles shrugs. “It went into testing a couple of weeks ago. There was a chance it wouldn’t work, though, and I didn’t want to get your hopes up unless I was sure it would, so I—”

Before he can finish that thought, Scott launches himself at Stiles, wrapping his arms tight around Stiles’s torso. “Shut up.” He squeezes Stiles like a plush toy. “You’re the best.”

“Yeah,” Stiles agrees, pressing his face into Scott’s shoulder. With his ear so close to Scott’s neck, he can hear the sound of gears turning like a steam-punk pulse under his synthetic skin. “You might wanna watch that extra strength though, buddy. I—uh. I can’t breathe.”

*

Stiles always finds it weird when he has to take Scott apart and lay him out like a collection of puzzle pieces on the table at the workshop. By the time he gets Scott’s chest panel open, Stiles doesn’t have anything that vaguely resembles a body in front of him anymore.

It makes him feel like a little kid again, playing at being a doctor, operating on an anesthetized patient he put together using whatever odds and ends he managed to find in the garage. To an outsider, he could be any engineer working on any project right now; looking at his workbench, no one would suspect that life can come from these metal parts.

Scott’s battery pack is under his ribcage. Stiles removes the wires around it carefully and sets it down on the bench. The reactor is sitting next to it, smaller and sleeker, roughly half its size and weight. Stiles runs his fingers over it slowly before he takes a deep breath and slots it into place.

This is the result of four years of research.

He knows it’s going to change everything for Scott.

All Stiles needs to do now is solder the wires to the circuit board, like veins running into a heart, and Scott will never have to act like the robot version of Cinderella again; no more disappearing on the stroke of midnight so he can get back to his charging station before his system goes into involuntary shut-down mode, and no more dependence on Stiles.

Scott will be his own power source.

The thought of that is exciting, because Scott will have so much more freedom like this, but also kind of terrifying, because, for the first time since Stiles switched him on, Scott won’t need Stiles anymore.

The thought of that leaves a hollow feeling in his chest.

Stiles shakes his head, flicks his soldering iron on, and gets back to work before his mind decides to wander again.

He enjoys soldering—likes how mindless and easy it is—but when Stiles has to do a lot of it at once, like he does now, the heat from the iron and the hiss of melting solder makes it feel like a much more gruelling process than it is.

Stiles is dripping with sweat before he’s even halfway done.

“You should really put your fan on if you’re using a soldering iron for an extended period of time,” someone tells him, approaching from behind.

Stiles startles so hard his fingers slip on the handle. The metal rod burns a shallow line across his palm. “Ouch, ouch, fuck,” he hisses, dropping the iron back in its stand so he can hold his hand up to the light and inspect the extent of the damage.

Derek is by his side in an instant. He grabs Stiles by the wrist, steers him over to the sink at the back of the room, turns the water on cold, and shoves Stiles’s hand under the stream.

“You need to be more careful with your tools,” Derek says flatly.

Stiles rolls his eyes. “You need to stop sneaking up on me.”

“I knocked,” Derek says, defensive. “It’s not my fault you didn’t hear me.”

“Maybe you should knock louder next time,” Stiles grumbles as he pulls his hand away from the faucet to give his fingers an experimental wiggle. His entire arm throbs in response.

Derek sighs and promptly pushes Stiles’s hand back under the water. “At least wait until it goes numb before you start moving it.”

Stiles pulls a face. “My hand is gonna be completely useless until the burn has blistered over,” he says. “Talk about the worst timing ever. Scott’s gonna kill me if I don’t finish his upgrade today.”

They have a deal: Scott lets Stiles upgrade his systems once a month, no complaints, but only on the condition that Stiles does whatever he needs to do as quickly as possible. He gets seriously irritated every time Stiles has to leave him switched off overnight.

Derek raises an eyebrow.

“Since when is your robot homicidal?”

“He’s not my robot,” Stiles snaps automatically, then huffs when Derek ducks his head to smirk at the floor. “Derek, come on, that isn’t funny,” Stiles says, and Derek outright laughs, so Stiles swats him hard in the shoulder with his uninjured hand. “I’m serious. Scott’s more than just a bunch of codes.”

Derek rolls his eyes.

“Fine. So, since when is Scott homicidal?”

“He isn’t homicidal,” Stiles says. “He’s tired of being a prototype.”

Derek frowns at the various parts of Scott that are assembled on the worktop.

“He wouldn’t be here if he weren’t a prototype.”

Derek doesn’t need to clarify that he means _here_ in the metaphysical sense.

Stiles had most of the complex programming for Scott’s mental systems figured out before he arrived at The Beacon, but he would never have been able to actually build Scott if the facility didn’t cover the cost of all his supplies; Scott wouldn’t exist if he weren’t a prototype.

“True,” Stiles allows. “But that doesn’t mean he’s happy about it. Do you remember how angry Scott was when the first version of the medical model went into production?”

“You mean the time he yelled at you to stop using him to build a master race of slaves?”

Stiles grimaces at the memory. “Yeah.”

Scott has come around to the idea that parts of his coding are used commercially now that he knows how different from him the final products are—how much less advanced—but when he first found out about the product launch from Boyd, of all people, he was so furious with Stiles that he tried to destruct his own system.

Thank god Stiles had the foresight to make him waterproof.

“I thought he got over that,” Derek says, his eyebrows bunching together in confusion. “You said he liked the idea of the final product being a personal health care assistant.”

“Yeah, he does,” Stiles says. “But now that I have models that are closer to the final product than he is, he thinks I should leave his codes alone. He wants a normal life.”

“So let him have one,” Derek says with a shrug.

“I’m trying to,” Stiles says. “I don’t use him to test codes for the production line anymore. But since I toned coding for emotion and independent thought back so much on the later versions, Scott is still the most advanced prototype I have. He’s—”

“Almost human,” Derek finishes for him.

“Yeah.”

Derek is one of the few people who knows that Stiles’s vision for the project, before he took the product down a commercial line, was to perfectly recreate the human form through coding and mechanics.

Scott is so close to being finished.

Stiles knows it’s selfish, but he needs Scott to stick this out for a few more months.

Derek turns to look at Stiles, fixing his eyes on him with a kind of intensity that makes Stiles feel like he’s been laid beneath a microscope for evaluation. “At least you think about his happiness,” he says. “Most people here wouldn’t.”

“I never used to,” Stiles admits. “When I made him it was like… like, I knew he’d be—you know. Like a person. But I never thought about how he’d feel about being a part of this.”

Derek places the flat of his hand of the small of Stiles’s back, warm and grounding. “Scott is lucky to have you,” he says, painfully earnest. Stiles feels his cheeks flush hot. “You could easily rewrite his codes so his personality is better suited to your research, but you haven’t done that. You care about him enough to listen to what he wants.”

Stiles stares at him.

Derek always seems to know the right thing to say to negate Stiles’s unspoken concerns about his own moral compass, but he rarely indulges Stiles with speeches like this.

“You’re kind of biased,” Stiles says eventually. “But thank you.”

Derek traces his hand up the curve of Stiles’s spine until it lands it on the back of his neck, then squeezes gently. “Stay here. I’m going to get something for your hand.”

It’s stupid, but Stiles can still feel the heat from his fingers long after he’s gone.

He pulls his hand out of the water and pokes at the tender flesh on his palm to distract himself from the ghost touch. It doesn’t hurt. His hand is too numb.

He splashes some water against his cheeks, shuts the tap off and goes back to the workbench. He isn’t careless enough to touch the soldering iron with an injured hand, so he starts to reassemble some of Scott’s other components instead.

Stiles has done this so many times by now that putting Scott back together after an upgrade is as familiar as building houses out of lego. He’s halfway through Scott’s left hand when Derek taps a sarcastic knock against the door.

“I thought I told you to stay where you were,” Derek says, closing the space between them in a handful of strides across the room.

Stiles hums a noncommittal response, then lets out an indignant squawk as Derek pries the parts he was fiddling with out of his grip, sets them down on the workbench and gently flattens Stiles’s injured hand against his palm. He traces the tip of his index finger along the line of the angry burn mark, frowning down at it, and Stiles lets out an involuntary shiver.

“Does that hurt?” Derek murmurs, pressing down ever so slightly on Stiles’s skin. Stiles’s throat suddenly feels ten times thicker than before. He can’t trust himself to speak, so he replies with a quick shake of his head. “That’s good. I’ll try to keep this quick.”

Derek drops Stiles’s hand so he can pull a tube out of his pocket, uncaps it, and squeezes some of its pale blue contents onto his palm. He gestures for Stiles to move his hand closer again, dips the tip of his finger in the salve, and applies a thin coat along the line of the burn.

“This might sting a little,” he warns Stiles just as a sharp wave of pain kicks in.

_A little_ doesn’t even begin to cover it. His skin feels like it’s on fire as the cream sinks into the burn. Stiles has to grit his teeth to keep himself from crying out.

The only thing that keeps him grounded through it is the soft press of Derek’s fingers against the back of his hand.

Then the pain is gone, replaced by the strange sensation of his skin knitting itself together again. The line of the burn glows red and hisses before it disappears, leaving nothing but newly healed skin in its place.

“Whoa,” Stiles breathes, holding his hand up to the light in disbelief. “What is that?”

Derek shrugs, recapping the tube and stuffing it back in the front pocket of his lab coat. “Healing balm. I’ve been working on it for a few weeks now.” As he speaks Stiles clenches and unclenches his hand, grinning stupidly when his palm doesn’t so much as twinge. “Does it feel better now?”

“It feels better than ever,” Stiles tells him. “That stuff is amazing.”

Derek directs another small smile at the floor. “Thank you.”

“So how are things going up in nano-tech anyway?” Stiles asks as he switches the soldering iron on again. The rest of the wiring shouldn’t take too long. If he works fast he can still get Scott up and running before dinner time.

Derek rolls his eyes. “That’s like me asking you how things are going in the robotics lab. I work in the pharmaceutical department of nano-tech, Stiles. I have no idea what the central nano-tech lab is even working on right now.”

“Okay.” Stiles untangles a clump of wires with one hand and reaches for a strip of solder wire with the other. “Then tell me how things are going in the pharmaceutical department.”

He listens to Derek talk while he finishes wiring the reactor into Scott’s chest.

*

Derek is still in the workshop when Scott is fully assembled.

He’s working on a sudoku puzzle he found in a month-old newspaper that was buried under a mountain of unfinished paperwork on Stiles’s desk. At some point Derek turned on the ceiling fan, and the corner of his page keeps on fluttering up in the breeze. Every so often he lets out a short, frustrated sigh, stuck on a number, and viciously clicks his pen against the tabletop.

Stiles catches himself smiling to himself every time Derek does it, even as he struggles to get Scott’s stiff limbs back into his clothes. Weirdly enough, this is the most difficult part of every upgrade. Scott hates waking up naked on the table—says it makes him feel like he’s about to get probed—but it’s almost impossible to move him unless his motion system is on, and his motion system only comes on if Scott is conscious, and Scott being conscious means Scott waking up naked, so Stiles sucks it up and works with what he’s got.

He’s in the process of tugging one of his old high school lacrosse jumpers over Scott’s head when he notices that Derek is staring at him. Stiles cocks an eyebrow back.

“What’s up with that face? Have you never seen a guy dress another guy before?”

“Not like that I haven’t,” Derek replies dryly. “Do you need any help?”

As helpful as having some help would be right now, Stiles knows that Scott hates the thought of anyone—including Stiles—touching him while his systems are down. It’s better to keep contact to a minimum.

“Thanks dude, but I’m good,” Stiles says as he yanks the jumper over Scott’s broad shoulders. “If you really wanna help, you can start my laptop for me.”

“Oh wow,” Derek deadpans as he reaches for Stiles’s satchel and pulls his laptop out. “That’s a lot of responsibility. You sure I’m up to the task?”

“I’m willing to take a chance on it,” Stiles tells him with a wink.

Derek snorts. “Easy, Casanova. Keep talking like that and I might swoon.”

“Are you flirting with me?” Stiles asks, narrowing his eyes at Derek.

“No,” Derek says, but his ears looks several shades pinker when he ducks behind Stiles’s laptop screen, hunches over the keyboard, and carefully taps a few keys. Then a few more. Then a few more. Stiles can’t see most of Derek’s face from where he’s standing, just his eyebrows sinking lower with each failed attempt. “Stiles, did you change the password on this thing?”

“Yeah, about a month ago.” Stiles makes a face as he eases a pair of loose sweatpants up Scott’s calves. “Erica kept changing my screensaver to some porn thing with two dudes in lab coats.”

Derek grimaces in sympathy. “I think I know the one.”

Stiles laughs, hoisting Scott’s legs over one shoulder so he can pull the pants all the way up. “Ugh,” he says, wrinkling his nose as he sets Scott down again. “I feel like a parent. I’m way too young for this.” He wipes his hands on his knees as he heads over to his desk, then casually leans against the back of Derek’s chair. “The new password is 04062011.”

Derek types the numbers as Stiles recites them, a fond smile on his lips. “Scott’s activation date,” he murmurs as the screen unlocks. “I should have guessed.”

Stiles gapes at him.

“I…” he starts, then stops. “How do you know that?”

The line of Derek’s shoulders goes stiff for a moment and then he shrugs, too casual.

“You threw him that ridiculous party in the breakroom last year. I remember it.”

Stiles feels his heart skip a beat.

It’s been ten months, and this is the first time Derek has mentioned the party. The party where Stiles made the mistake of letting Erica mix his drinks, slammed way too many shots, attempted to start a fight with a pot-plant, and then insisted on spending the rest of the night sprawled out across Derek’s lap.

He woke up to several blurry pictures of Derek scowling while Stiles hides his face against his neck—all courtesy of Allison—and at least thirty different _did you get finally laid?_ texts.

The answer to that question is a resounding no. Far from it. Derek couldn’t have made it more obvious that he’s not interested. Sure, he carried Stiles back to his room when the party wound down, tucked him into bed, and left a glass of water and a bottle of Advil on the nightstand, but that stuff doesn’t mean anything.

Derek would have done that for anyone.

And Stiles should have known. Shouldn’t have let himself hope, even a little bit, that there might be something there. At least then he’d have been prepared for Derek to shut him down without a moment of hesitation when Stiles turned up at his lab to talk about it.

“Stiles,” Derek said before Stiles could get a word out. “It’s fine. We’re fine. You don’t have to say anything more about it. You were drunk. Let’s just forget it. Could you pass me that petri-dish?”

Things had been awkward for about a week afterwards. Stiles moped, Derek avoided him, and Scott held a not-so-secret secret meeting to warn everyone to stop talking about it. Then Derek ran into an obscure problem with the security system that Stiles built for him, and Stiles was the only person who could fix it, so Stiles had to stop moping and Derek had to stop avoiding him.

Stiles spent four hours in his lab tweaking the codes until they worked again, and Derek spent all four of them rambling about complex equations and microscopy like nothing had ever happened.

After that things went back to normal.

Until ten seconds ago, Stiles was convinced that Derek had forgotten about it, but that clearly isn’t the case. Derek is staring at the desktop screen on the laptop way too intently for Stiles to believe  he doesn’t know exactly which can of worms he just busted open.

Stiles squints at him, trying to get a read on what Derek wants from him, but Derek’s expression remains carefully blank under his scrutiny.

“Um,” Stiles says slowly.

There are a million things he wants to say to Derek, but he’s too conscious of the fact that he’ll never be able to un-say them to get any of the important stuff out. “Okay,” is what he settles on. “I’m gonna reboot Scott’s system now.”

Stiles knows he’s taking the coward’s way out here, but he can’t bring himself to care. He isn’t ready for Derek to break his heart again.

“Oh. Yeah, you should probably—” Derek scoots back in his chair until he isn’t blocking Stiles’s access to the laptop anymore then gestures for Stiles to go ahead and use it.

Stiles still has to lean over his shoulder to reach the trackpad. He ends up hovering so close to Derek that he can hear each rise and fall of his shallow, unsteady breaths.

It’s distracting. Stiles fumbles to get the program open, rushes through typing out the basic commands, then backs the hell away before his own breathing pattern can sync with Derek’s.

He can hear the faint whirr of Scott coming back to life behind him, so he turns and busies himself watching that. Even after four years, it still amazes Stiles to watch Scott’s wire and metal skeleton transform into something recognisably human as the nanobot program conceals all his oddities under a layer of synthetic skin.

This was the first program Derek developed at the facility. He only wanted it to provide seamless cover for burn marks and other untreatable scars, but time has proven it much more useful than that. The DNA software the program uses to get an exact skin match with the patient is now used by the secret services, medical practitioners, the police force and the cosmetics industry.

Derek stopped working on the software shortly after it took off, concerned by its unprecedented commercial success, but he made an exception for Stiles and Scott. He spent weeks rewriting the code to hypothetical genomes, helped Stiles choose Scott’s biological parents—a nurse and a low ranking FBI agent—from the gene-bank in the biomedical center, and installed the system a week before Stiles activated Scott for the first time.

When Scott woke up with dimples, tanned skin, floppy hair, and a slightly uneven jawline, Stiles had been so overwhelmed and exhausted he actually cried in delight. Derek had stiffened beside him, obviously uncomfortable, but he laced his fingers with Stiles’s and let him cling to his hand like a lifeline anyway.

Stiles is pretty sure that that’s the moment he fell in love.

Today feels a lot like the first time—him and Derek alone in the workshop, a sense of expectation in the air between them as they wait to see whether or not this is going to work.

So far Scott seems to be starting up as usual, but Stiles can’t trust that this is working until all his systems are on. The reactor is far more powerful than the battery pack. One misplaced wire and Scott could blow a fuse, short-circuit and spontaneously combust.

“Hey,” Derek says, approaching Stiles from behind. “Don’t be nervous. This will be fine.”

Stiles knows—objectively—that Derek is right. The reactor has been through more trials and tests than most products designed for the mass market. Stiles had to be certain it would be safe before he let it anywhere near Scott.

“I’m just worried,” Stiles admits.

“There’s no need to be.” Derek squeezes his arm. “See?”

As Derek talks Scott’s eyelids flutter open. He lets out a low groan, throws an arm over his face to shield his eyes from the glare of the bright overhead light, and turns his head just enough to shoot a scowl at Stiles.

“Dude, come on,” he grumbles half-heartedly. “You know my eyes are practically human levels of sensitive. The least you could do is dim the lights before you wake me up.”

Stiles rolls his eyes, ignoring him in favor of placing his hand flat on Scott’s chest. He can feel the reactor thumping steadily beneath his palm, expanding and contracting like a human heart.

Scott pushes himself up on his elbows so he can look too.

“Well?” he asks, eager. “Is it working?”

“I—” Stiles starts, but he chokes on the words before he can get them out. He swallows thickly, blinks hard then tries again. “Yeah, Scotty. I think it is.”

*

The reactor means Scott won’t have to come back to the workshop to recharge at night anymore. He can still activate sleep mode at night if he wants to, but he won’t need it. In fact, Scott won’t have to worry about his batteries running out ever again.

Naturally—this being Scott—the only thing he’s interested in doing with his improved battery life is spending an entire night with Allison for the first time. Once Stiles has run through his standard set of post-update tests to check everything is working correctly, he tells Scott he’s free to go.

Scott can’t get out of the workshop fast enough.

“Let’s hope he covers up,” Stiles jokes as the door swings shut behind Scott. “I’m not old enough to deal with Scott’s robotoid babies.”

Derek tilts his head to the side. “Could that actually happen?”

“What?”

“Robotoid babies,” Derek clarifies. “Could Scott and Allison have kids?”

“Oh.” Stiles feels his face pink up. “Um. Not right now they couldn’t. I mean, Scott can—you know.” Derek smirks when he makes a lewd gesture with his hand. “But Scott doesn’t have any functional reproductive organs in that sense. I have no idea how to make something like that.”

Derek hums, thoughtful.

“I could help you with it if they ever decide they want kids.”

Stiles turns to stare at him, open mouthed. “Derek, are you serious?”

“I’m hoping to make a start on a more accessible and reliable alternative to infertility treatment anyway,” Derek admits. “And if that’s something Scott and Allison want, then yeah, of course I’ll try my best to make it happen. It shouldn’t be too hard to tweak the codes for it.”

“You would do that for them?”

“For them,” Derek repeats, the corners of his lips twitching a fraction, and when he catches Stiles looking at his mouth, he smirks drops his eyes to the bowed curve of Stiles’s lips. “For you.”

Stiles is suddenly hyper-aware of how close to him Derek is. He doesn’t remember which of them closed the distance, but there’s barely a foot between them now, and all Stiles can feel is the heat from Derek’s skin.

“Oh my god,” Stiles says before he can stop himself. “Are you gonna kiss me?”

Derek is out of his space in an instant. “Fuck.” He scrubs a hand down the side of his face. “Stiles. I’m so sorry. I shouldn’t have overstepped your boundaries like that. I know you don’t—but for a minute I thought—and then recently you seemed—but that isn’t an excuse, I’m—”

Stiles blinks back at him.

He feels like he’s just been sucker-punched with information. At the rate Derek is throwing it at him, there’s no way Stiles can take it all in.

“Derek, stop,” he interrupts. “I’m gonna need you to calm down. Okay?”

Derek looks like he wants to argue, but for once he doesn’t. He just closes his eyes and draws in a series of deep, carefully measured breaths.

“Okay,” Stiles continues when the tightness in Derek’s shoulders has eased up a bit. “Now tell me everything you just said again, only this time try to use full sentences.”

Derek grimaces. “I’m sorry for making you uncomfortable,” he says, fixing his eyes on the wall behind Stiles’s head. “I just got caught up in being here with you. Sometimes I forget that we’re not…”

He trails off, making a vague gesture with his hands.

“So you _were_ gonna kiss me,” Stiles says.

Something in his tone makes Derek brave enough to chance a glance over at him.

His eyes widen at the thunderstruck expression on Stiles’s face.

“Stiles,” he breathes. “Are you—I mean, yes. I was gonna kiss you. I was gonna—”

Stiles is on him before he can get the rest of the sentence out. He backs Derek against the nearest workbench, pins him there with his hips, then loops both of his arms hands around Derek’s neck. “Well,” he says, arching an eyebrow expectantly. “Are you gonna finish what you started or not?”

Derek cups gentle fingers around his jaw and pulls Stiles in closer, closer, and their noses bump together before Stiles remembers to tilt his head. Derek huffs a laugh, nuzzles Stiles’s cheek, and his lips brush feather light against the corner of Stiles’s mouth.

“You’re supposed to kiss me properly,” Stiles protests.

Derek makes a soft noise in the back of his throat.

“Maybe I want you to kiss me.”

Stiles doesn’t need to be asked twice.

He tilts his head so he can catch Derek’s lower lip with his mouth, presses closer, swallows the small moans that Derek makes, and pulls away when he feels Derek smile against his lips.

Derek makes a low keening noise at the loss of contact, knots a hand through the back of Stiles’s messy hair, and pulls him in again, sealing his lips over Stiles’s with a hot, open-mouthed kiss.

He kisses the way Stiles always thought he would—full-bodied, tender and imposing. His tongue pushes into Stiles’s mouth, hot and demanding, and the hand he doesn’t have clenched in Stiles’s hair wanders down to settle on Stiles’s hip.

His fingertips nudge the hem of Stiles’s shirt up as he pulls Stiles closer to him.

“Stiles,” Derek says, his voice rougher than Stiles has ever heard it. “Wait.” He pulls back enough to drop his head onto Stiles’s shoulder and drops a chaste kiss against his collarbone. “This is good, you’re so good, and I want—” he cuts himself off, presses a kiss to Stiles’s throat, and lifts his head so Stiles can look at him. “Want you. So much. But we should probably talk about this.”

“Nope,” Stiles says, pawing at the button on Derek’s stupidly tight jeans. “We can talk later.” He presses a clumsy kiss against Derek’s chin, fumbles the button open, and sneaks his fingertips under the waistband of Derek’s boxer briefs. “Now shut the hell up and let me have this.”

Derek does.

*

They end up curled up on together in the cot that Stiles had set up in the corner of his workshop two years ago, after he spent three consecutive nights crashing on his desk while he to repair a fault in Scott’s circuitry that left him non-responsive for almost a week.

The bed is too small for both of them to fit comfortably, but Derek is yet to complain about it, and until he says something, Stiles is going to stay exactly where he is, sprawled out on top of him, the side of his face smushed against Derek’s bare chest.

They’re holding hands, sort of, if the way Derek alternates between tracing patterns against the back of Stiles’s hand and playing with his fingers counts as hand holding, and though neither of them has spoken for a while, the silence is weirdly comfortable.

But Stiles can tell that Derek is itching to talk about this.

“Okay then, big guy,” Stiles says, propping himself up on his elbows so he can peer down at Derek and his stupidly beautiful face. “I know you probably have some kind of speech prepared for this, since you spent most of the post-coital bliss period making weird faces at the ceiling, so feel free to lay it on me or whatever.”

Derek snorts quietly.

“That’s not quite the romantic opening I was hoping for.”

Stiles rolls his eyes, dips his head, and catches Derek’s lips in a soft kiss.

“Better?”

Derek tilts his head like he has to think about it, wraps his arms around Stiles’s shoulders to stop him from moving, and stretches up to kiss him again.

“Better,” Derek confirms after a moment, which is so corny and awful that Stiles has to bite his lip to stop himself from laughing at him. “But I don’t have a speech prepared. I just—I really like you, Stiles. Kind of a lot.”

“I like you too,” Stiles says instantly. “So much.”

“Good,” Derek says, like that comes as a surprise to him. “That’s good.”

Maybe this is the point where Stiles should tell Derek that he’s been ass-over-heels in love with him for the better part of the last five years. That he’s wanted to kiss Derek from the moment he first set eyes on him.

It was his first weekend at The Beacon, and Stiles was scheduled for a day off, so he decided to explore the building a little. He maintains to this day that it wasn’t his fault that he got lost and somehow ended up in the middle of the pharmaceutical department; it wouldn’t have happened had anyone bothered to give him a proper tour of the place when he arrived.

Which is what Stiles told Derek when he found him wandering through the empty labs, looking for someone to give him directions out of there, and snapped that Stiles should stay away from other departments in the future before he grouchily escorted Stiles back to his corridor.

And Stiles had spent the rest of the evening obsessing over it.

But, for now, Stiles holds off on the heavy confessions.

They have plenty of time for stuff like that later.

Stiles is happy to take this slow.

Well…

Slow-ish.

“So, when do I get to tell everyone that you’re my boyfriend?” he asks Derek. “Because, dude, I get it if you want to keep this on the down-low until we’ve been together for a respectable amount of time or whatever, but I really want to tell everyone that you’re my boyfriend. Like, right this second. Immediately.”

Derek pulls Stiles back down on top of him.

“Sleep first,” Derek says, pressing a kiss to Stiles’s temple. “You can tell everyone later.”

*

“So,” Stiles says, throwing open the door to the break room the next morning. “Derek and I are officially together. As in dating together. Boyfriend and boyfriend.” He pulls Derek through the door after him, throws an arm around his shoulder, and presses a quick kiss against his stubbly cheek. “So you guys are gonna have to get used to the fact that we’re a couple now.”

“That’s great,” Allison tells them earnestly. “We’re all so happy for you!”

Isaac snorts, not bothering to look up from his solo game of Mario Kart.

“Please,” he says dismissively. “This isn’t news. You think I’d have put up with Stilinski for this long if I didn’t know that you two are part of some kind of weirdo package deal?”

Erica purses her lips as she passes a twenty dollar bill over to Boyd. “Seriously. You couldn’t have kept it in your pants two weeks longer? I was so close to winning the betting pool this time.”

“You’re never going to win the betting pool, Erica,” Boyd says bluntly, folding her money into neat quarters and tucking it into his pocket. “I don’t know why you even try.” He shoots a careful smile at Stiles and Derek. “Thanks for the perfect timing, guys.”

“It’s about time,” Lydia smirks at them over her mug of chamomile tea. “I was starting to think we’d have to stage some kind of intervention to get you together. Congrats on the sex, guys.”

Scott narrows his eyes at Stiles. “You better not have had sex in our workshop.”

“We didn’t,” Derek tells him quickly.

“Uh, yeah, we did,” Stiles says.

Scott presses a hand to his chest where his brand new reactor sits, looking period-drama levels of betrayed and scandalized. Allison laughs, Erica swats at Boyd’s shoulder in a full-body move that causes Isaac to drive off the side of the road, landing him in eighth place, and Lydia rolls her eyes at them theatrically.

While everyone else is distracted, Derek reels Stiles towards him and kisses him.

Stiles smiles back at Derek, a small and private smile in the middle of the chaos, and thinks that maybe, if he were a projectile and happiness were a quantifiable force, the trajectory graph of his life is probably heading for a pretty steep upward curve.

**Author's Note:**

> the reactor stiles builds for scott is loosely (read: completely) based on tony stark's arc reactor from iron man, and the final product that stiles puts out on the market is a smaller, less adorable version of baymax from big hero six.
> 
> i'm [falsealpha](http://falsealpha.tumblr.com/) on tumblr if you ever want to chat! or you could go all out and [send me a prompt](http://falsealpha.tumblr.com/prompts).


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